Absorption Engineering in an Ultrasubwavelength Quantum System

Abstract

Many photonic and plasmonic structures have been proposed to achieve ultrasubwavelength light confinement across the electromagnetic spectrum. Notwithstanding this effort, however, the efficient funneling of external radiation into nanoscale volumes remains problematic. Here, we demonstrate a photonic concept that fulfills the seemingly incompatible requirements for both strong electromagnetic confinement and impedance matching to free space. Our architecture consists of antenna-coupled meta-atom resonators that funnel up to 90% of the incident radiation into an ultrasubwavelength semiconductor quantum well absorber of volume V = λ310–6. A significant fraction of the coupled electromagnetic energy is used to excite the electronic transitions in the quantum well, with a photon absorption efficiency 550 times larger than the intrinsic value of the electronic dipole. This system opens important perspectives for ultralow dark current quantum detectors and for the study of light–matter interaction in the extreme regimes of electronic and photonic confinement.

High temperature metamaterial terahertz quantum detector

“…As in Ref. [2] we found that the radiation loss LC of the LC structures are negligeable, and they have non-radiative linewidth of LC=0.4 THz. By studying uncoupled LC resonators alone, we found that the annealing of the ohmic contacts introduces a frequency shift fLC=+0.56 THz that is taken into account in the final modelling shown in Figure 2.…”

“…The fabrication procedure closely resembles the one described in Refs. [1,2], but has been adapted to improve the optical quality of the sample while coping with the high temperature annealings necessary to obtain ohmic contacts between the active region and the metallic parts.…”

“…In Ref. [2] we have discussed in details the coupling between the LC resonators and the antenna elements. This coupling is described in terms of the temporal coupled mode theory [4], where the LC resonator and the antenna are treated as two coupled oscillators described by their frequencies, radiative and non-radiative loss rates: respectively (LC, LC, LC) and (A, A, A).…”

“…The terahertz (THz) domain of the electromagnetic spectrum has well defined applications ranging from imaging, security, spectroscopy [1], and has been recently envisioned for future 6G wireless communications by Samsung [2]. Quantum detectors based on electronic transitions in semiconductor quantum wells, QWIPs [3,4] have many assets for advanced applications, as they combine high speed and high quantum efficiency.…”

Unified Description of Saturation and Bistability of Intersubband Transitions in the Weak and Strong Light-Matter Coupling Regimes

“…1(a). In the case of the ISB system, the radiative coupling of the ISB transition to free-space radiation is negligible [31,32]. The coupled system's response to an external excitation is given by…”